CSB327 Lecture 6 Summary

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Cell and Systems Biology
Maurice Ringuette

CSB327 Lecture 6 Notes - Organization of the kidney o Nephron is the basic and functional unit of the kidney  There are one million nephrons in each kidney  Contains a glomerular (Bowman’s) capsule that surrounds a glomerulus (group of capillaries)  Two specialized cells associated with the glomerulus  Inside the glomerular capillaries is an endothelium (endothelial cells) o Cells are fenestrated to allow direct contact between the contents of the blood and the GBM o The GBM is exposed to the contents of the blood  Outside the glomerular capillaries are podocytes (visceral epithelial cells) o Cells have feet-like processes o Adjacent podocytes are bridged by filtration slits, which as act as a physical barrier to prevent diffusion of serum proteins into the Bowman’s capsule  Filtration slits impart a size selection (>30 kDa)  Both contribute to making the glomerular basement membrane  The GBM provides support and barrier functions to the glomerulus  Organized into three distinct layers o Lamnina rara externa (facing podocytes) o Middle lamina densa (thickest)  Composed of ype IV collagen  Enriched in negatively charged sugars, which prevent the filtration of negatively charged proteins by charge repulsion (because most serum proteins have an overall negative charge) o Lamina rara interna (facing endothelial cells)  Highly negatively charged  Thicker than most capillary BM  The α1α2α5α6 network is found in the GBM that underlies the Bowman’s capsule epithelium  There is a switch in type IV collagen network in the GBM found between podocytes and endothelium  The α1α2 network is found in embryonic GBM  The α3α4α5 network replaces the α1α2 network in adult GBM o Interlinked by disulfide bridges that promote supercoiling of the network and increased tensile strength  Abnormalities in the structure of the GBM is responsible for kidney diseases  Characterized by an excess loss of protein in the urine  ALPORT SYNDROME  genetic defect  often fatal o Mutation in genes encoding for the α3, α4, or α5 (IV) chains o More common in males because COL4A5 gene is in the X chromosome o Males and females equally affected if COL4A3 or COL4A4 gene because is located on autosomes  X-linked Alport  mutation in α5(IV) chain  Autosomal Alport  mutation in α3(IV) or α4(IV) chains o GBM is composed of α1α2 network instead of α3α4α5 network  Cannot withstand the glomerular pressure  Results in ESRD in early teens or twenties  GOODPASTURE’S SYNDROME  rare autoimmune disease  can be cured using immunosuppressant o Associated with the development of anti-GBM autoantibodies o The immune system attacks the GBM and the alveoli and capillaries of lungs o The antibodies trigger inflammation that interferes with kidney and lung function o The autoimmune reaction targets the α3(IV) chain o Results in destroying Bowman’s capsule and deposition of anti-type IV collagen IgG - Organization of skin o Largest organ in our body o Two layers are epidermis and dermis o DEJZ separates the dermis and epidermis  Basement membrane  Anchoring fibrils made of type VII collagen  Basal lamina o Anchoring fibrils  Adhesive structures that ensure the connection of the epidermal BM with the
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